SW82

Location: Warncoort

Australian Soil Classification: Vertic (& Sodic), Calcic, Black CHROMOSOL


General Landscape Description: Gently undulating plain.
Site Description: Puff of a gilgai.
Geology: Basalt plain.

Soil Profile Morphology:

Surface Soil

A1	0-10 cm	Very dark brown (10YR2/2 moist); loam; pH 5.5; clear change to:	SW82 Profile. Note: Surface (A1) horizon has been stripped from the soil profile
Subsoil
B21	10-40 cm	Very dark grayish brown (10YR3/2 moist); medium heavy clay; medium to fine (5-20 mm) polyhedral structure; strong consistence dry; pH 5.8; gradual change to:
B22	40-90 cm	Dark grayish brown (10YR4/2 moist) and brownish yellow (10YR6/6) mottles; heavy clay; some pockets of fine buckshot; coarse prismatic, parting to fine lenticular structure; strong consistence dry; pH 6.8; abrupt change to:
B23ssgk	90 cm+	Dark grayish brown (10YR4/2 moist) with brownish yellow (10YR6/6 moist) and very few (<2%) light olive brown (2.5Y5/4 moist) mottles ; medium (20-50 mm) prismatic structure; strong consistence dry; very few (<2%) soft carbonate segregations; strongly vertic; pH 8.5.

SW82 Profile wider view.

• Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.
• Colour contrast in deeper subsoil.

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	Strongly Acid	Low	Non-Sodic	None
Subsoil (B21 horizon)	Moderately Acid	Very Low	Non-Sodic	None1
Deeper Subsoil (at 90+ cm)	Moderately Alkaline	Low	Strongly Sodic	Strong - Complete
1 Slight dispersion after remoulding.

The surface soil is strongly acid. The subsoil is moderately acid becoming moderately alkaline with depth.

Salinity rating is low in the surface becoming very low in the subsoil.

The soil is non sodic in the surface and upper subsoil and strongly sodic in the deeper subsoil.

The clay content increases markedly at the A/B boundary.

Horizon	Sample Depth (cm)	pH (water)	pH (CaCl2)	EC 1:5	NaCl %	Exchangeable Cations
						Ca	Mg	K	Na
						meq/100g
A1	0-10	5.5	4.9	0.21		6.2	3.2	0.61	0.37
B21	10-40	5.8	4.8	0.1	<0.01	7.2	7.9	0.4	0.5
B22	40-90	6.8	5.6	0.09		7.9	13	0.41	1.8
B23	90+	8.5	7.3	0.17		6.5	12	0.27	3.2

Horizon	Sample Depth (cm)	Exchangeable Aluminium mg/kg	Exchangeable Acidity meq/100g	Organic Carbon %	Nitrogen %	Field Capacity pF2.5	Wilting Point pF4.2	Coarse Sand (0.2- 2.0 mm)	Fine Sand (0.02- 0.2 mm)	Silt (0.002- 0.02 mm)	Clay (<0.002 mm)
A1	0-10	<10	12	3.8	0.29	25.6	10.8	23	37	14	21
B21	10-40	18	15			39.6	24.6	13	21	7	56
B22	40-90		12			45.5	26.7	11	16	6	63
B23	90+							18	25	7	48

Management Considerations:

Subsoil (B) Horizons

• This profile is the “puff” of a gilgai soil. See GP 83 for a description of the associated “hollow”.
• The subsoil displays vertic features (i.e. slickensides) which indicates that significant shrinking and swelling occurs during wetting and drying cycles. This may have engineering implications and is likely to explain the variability in surface horizon depth across the trench.

• Between Aireys Reserve Rd and Birregurra Creek soil has coarse prismatic subsoil, very gilgaied, some patches of soft calcium carbonate (CaCO₃) below 1 m. Abrupt A2/B boundary. Deeper material grey/yellow mottled clay with fine quartz gravel >10 mm, rounded, below 1.5 m (<5% of matrix). Some (occasional) fragments of ferrguniated sandstone (<50 mm) in subsoil, but rare.